Query the boolean value at key

Property definitions

glesv2 $ GLES :: get_bool
	# Query the boolean value at `key`
	private fun get_bool(key: Int): Bool `{
		GLboolean val;
		glGetBooleanv(key, &val);
		return val == GL_TRUE;
	`}
lib/glesv2/glesv2.nit:808,2--813,3